Currently a microchip array of LED devices has drawn much attention due to its application to detectors, imaging sensors, and micro-displays. While microchip array LEDs are promising as a light source for micro-displays, several aspects may be problematic.
For example, the light energy from each LED device should be directed to an observer efficiently, i.e., the light should be collimated after it is emitted by LED devices. FIG. 1 illustrates a conventional solution for collimating light from LED devices. An array of microlenses 100 formed on LED devices 102 is proposed by Choi et al. in a paper at Phys. Stat. Sol. (c) 2, No. 7, 2903-2906, Mar. 11, 2005. A light 101 emitted from LED devices 102 can be focused to a focal point at an observer and the energy efficiency can thereby be improved. However, LED device 102 can laterally emit a light beam 104 to a nearby LED device possibly causing optical cross-talk. Such optical cross-talk may degrade the color saturation of the LED devices.
To solve the optical cross-talk problem, U.S. Pat. No. 6,882,101 proposes a structure shown in FIG. 2. An opaque material 202 is filled between LED devices 204 formed on a substrate 200. Lateral emissions of light from LED devices 204 can thereby be absorbed by the interposed opaque material 202 and an optical cross-talk can be reduced. However, since lateral light emitted by each LED device 204 is absorbed, this lateral light energy can not be used for display, and the energy efficiency is lowered.